Program to check your memory sticks:
/http://www.memtest86.com/
About the performance gain:
you will get an incredible boost,but only if you don't forget to connect a power cord to your 5900XT...
I have an Athlon XP2600 with 1GB PC3200 memory, running dual channel and replaced my GF4 TI4200 with an FX 5900XT ........my 3dmark 2001 SE score jumped up from +/- 10,200 marks to 13,500 without any overclocking.
Since a GF2 is older than a TI4200,I suspect that you gain even more than the 30% performance I did...
